[CI] add github action

Author: KihongHeo

.github/workflows/build.yml

@@ -0,0 +1,34 @@
+name: build
+
+on: [push, pull_request]
+
+jobs:
+  check:
+    name: build
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up OCaml
+        uses: ocaml/setup-ocaml@v2
+        with:
+          ocaml-compiler: 4.13.1
+
+      - name: Use cached dependencies
+        id: cache-opam
+        uses: actions/cache@v3
+        env:
+          cache-name: cache-opam
+        with:
+          path: |
+            ~/.opam
+            ./_opam
+          key: ${{ env.cache-name }}-build-${{ hashFiles('opam', 'build.sh') }}
+          restore-keys: |
+            ${{ env.cache-name }}-build-${{ hashFiles('opam', 'build.sh') }}
+            ${{ env.cache-name }}-build-
+
+      - name: Build CIL
+        run: |
+          ./build.sh || eval $(opam env) && make

build.sh

@@ -0,0 +1,2 @@
+opam pin add prosys-cil . -y
+make